linux-kernel - Re: [PATCH v3 13/21] slab: remove defer_deactivate

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Message-ID: <aW8W8xEMJegAzVgE@hyeyoo>
Date: Tue, 20 Jan 2026 14:47:31 +0900
From: Harry Yoo <harry.yoo@...cle.com>
To: Vlastimil Babka <vbabka@...e.cz>
Cc: Petr Tesarik <ptesarik@...e.com>, Christoph Lameter <cl@...two.org>,
        David Rientjes <rientjes@...gle.com>,
        Roman Gushchin <roman.gushchin@...ux.dev>, Hao Li <hao.li@...ux.dev>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Uladzislau Rezki <urezki@...il.com>,
        "Liam R. Howlett" <Liam.Howlett@...cle.com>,
        Suren Baghdasaryan <surenb@...gle.com>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Alexei Starovoitov <ast@...nel.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, linux-rt-devel@...ts.linux.dev,
        bpf@...r.kernel.org, kasan-dev@...glegroups.com
Subject: Re: [PATCH v3 13/21] slab: remove defer_deactivate_slab()

On Fri, Jan 16, 2026 at 03:40:33PM +0100, Vlastimil Babka wrote:
> There are no more cpu slabs so we don't need their deferred
> deactivation. The function is now only used from places where we
> allocate a new slab but then can't spin on node list_lock to put it on
> the partial list. Instead of the deferred action we can free it directly
> via __free_slab(), we just need to tell it to use _nolock() freeing of
> the underlying pages and take care of the accounting.
> 
> Since free_frozen_pages_nolock() variant does not yet exist for code
> outside of the page allocator, create it as a trivial wrapper for
> __free_frozen_pages(..., FPI_TRYLOCK).
> 
> Signed-off-by: Vlastimil Babka <vbabka@...e.cz>
> ---
>  mm/internal.h   |  1 +
>  mm/page_alloc.c |  5 +++++
>  mm/slab.h       |  8 +-------
>  mm/slub.c       | 56 ++++++++++++++++++++------------------------------------
>  4 files changed, 27 insertions(+), 43 deletions(-)
> 
> index b08e775dc4cb..33f218c0e8d6 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -3260,7 +3260,7 @@ static struct slab *new_slab(struct kmem_cache *s, gfp_t flags, int node)
>  		flags & (GFP_RECLAIM_MASK | GFP_CONSTRAINT_MASK), node);
>  }
>  
> -static void __free_slab(struct kmem_cache *s, struct slab *slab)
> +static void __free_slab(struct kmem_cache *s, struct slab *slab, bool allow_spin)
>  {
>  	struct page *page = slab_page(slab);
>  	int order = compound_order(page);
> @@ -3271,14 +3271,26 @@ static void __free_slab(struct kmem_cache *s, struct slab *slab)
>  	__ClearPageSlab(page);
>  	mm_account_reclaimed_pages(pages);
>  	unaccount_slab(slab, order, s);

As long as the slab is allocated with !allow_spin, it should be safe to
call unaccount_slab()->free_slab_obj_exts().

Looks good to me,
Reviewed-by: Harry Yoo <harry.yoo@...cle.com>

-- 
Cheers,
Harry / Hyeonggon